Conventional building practice for residence housing and small commercial buildings has in the past relied primarily on wood frame construction in which the building frame is constructed on site from framing lumber cut to fit piece-by-piece individually. It is a labor-intensive process and demands considerable skill from the carpenters to produce a structure that has level floors, perfectly upright walls, square corners and plumb door and window openings. Even when the building frame is constructed with the requisite care and skill, it can become skewed by warping of the lumber, especially modern low grade lumber produced on tree farms with hybrid fast-growth trees.
Although conventional wood frame buildings require very little equipment for construction, they have become quite costly to build. The labor component of the cost is substantial, partly because of the wages that must be paid for the laborious process of constructing the frame, and partly because of the many government mandated extra costs such as workman's compensation and liability insurance, social security payments, medical insurance premiums, and the host of reports that must be made to the Government by employers. Accordingly, employers now seek to minimize their work force by whatever means is available to minimize these burdensome costs.
Steel frame construction, usually referred to as “red iron” construction, is commonly used on commercial buildings because of its greater strength, fire resistance and architectural design flexibility. The parts of such a steel frame are typically cut and drilled to order in accordance with the architect's plans, then trucked to the building site and assembled piece-by-piece with the use of a portable crane. The building can be made precisely and as strong as needed, but the cost is relatively high because of the costly materials and the skilled crew and expensive equipment need to assemble the building. It is a construction technique generally considered unsuitable for single family residence building because the cost is high and the building walls are substantially thicker than those made using standard frame construction, so standard door and window units do not fit properly and must be modified with special trim that rarely produces the desired aesthetic appearance.
Earthquake damage is becoming a matter of increasing concern among homeowners because of the publicity given to damage and loss of life in recent earthquakes in the U.S. and abroad. Earthquake preparedness stories and advice abound, but an underlying unresolved concern is that conventional wood frame homes in the past were not built to tolerate the effects of an earthquake, neither in its ultimate load-bearing capability nor its post-quake serviceability limits. Modern building codes attempt to address this concern, but the measures they require add to the already high cost of a new home and may not always provide significantly improved resistance to earthquake damage, particularly with respect to after-quake serviceability.
Fire often follows an earthquake, as happened in the disastrous Kobe earthquake of 1994, and of course fire is a major threat to homes independent of earthquake. When fire breaks out in a conventional home, the wood frame fuels the fire and reduces the chances of successfully extinguishing it before the entire structure is destroyed. The major life saving advance in the recent past is the fire alarm which detects the fire and alerts the occupants that a fire has started so they may escape before burning up with the house, but significant improvements to the fire resistance of the home itself that would retard the spread of the fire would be desirable.
The other major catastrophic threat to homes is wind. Wind loads on wood frame homes have destroyed many homes, primarily because the roof is usually attached so weakly to the walls that the combination of lift, exerted upward on the roof by the Bernoulli effect of the wind flowing over the roof, and pressure under the eves tending to lift the roof off the walls, wrenches the roof off the walls and allows the wind to carry the roof away like a big umbrella. Without the roof, the walls of the house collapse readily under the wind load, completing the total destruction of the house.
Termite and carpenter ant damage to wood frame homes is a major form of damage, costing many millions of dollars per year. Although the damage done by insects is rarely life threatening, it is actually more extensive in total than the combined effects of wind and earthquake, and it is an ever-present danger in many parts of the country.
These and other problems with wood-frame construction have made the insurance costs for new buildings, particularly for multi-story residential construction such as apartment and nursing home construction, increasingly expensive.
Thus, there has existed an increasing need for a home building frame design that would enable the inexpensive construction of homes that are highly tolerant of the effects of earthquakes, do not support combustion, are capable of withstanding high winds, are immune to damage from insects, and can use standard building components such as door and window units. Such a building frame concept would be even more commercially valuable if it were possible to erect the building in a short time with a small crew and without heavy equipment, and the frame could be adapted to produce buildings of attractive building styles desired locally. Such a building frame is disclosed in U.S. Pat. No. 6,003,280 issued to Orie Wells on Dec. 21, 1999, and in U.S. Pat. No. 6,460,297 issued to Delton J. Bonds on Oct. 8, 2002, both of which are assigned to the assignee of this application. However, numerous improvements were found to be desirable in the building frame system shown in those patents for improved design flexibility, fabrication economy, ease of assembly and improved structural strength and resistance to adverse environmental conditions. Multi-story construction with concrete floors flush with top of frame and linked together by rebar extending through holes in the interior wall frames or by joists attached to support the floor and to structurally link the opposed walls to provide in-plane shear transfer and diaphragm continuity in and through the entire wall frame, and frames stacked vertically and bolted together w/o crushing the frame members would improve the structural strength of the building frame, and frame modules insulated from interior furring channels would improve the sound and thermal insulation of the interior and external walls of the building. These and other improvements would make the building system disclosed in these two patents even more desirable.